Electronic devices with reflective chamfer surfaces

ABSTRACT

The embodiments described herein relate to methods, systems, and structures for cutting a part to form a highly reflective and smooth surface thereon. In some embodiments, the part includes substantially horizontal and vertical surfaces with edges and corners. In described embodiments, a diamond cutter is used to cut a surface of the part during a milling operation where the diamond cutter contacts the part a number of times with each rotation of the spindle of a milling machine. The diamond cutter has a cutting edge and a land. The cutting edge cuts the surface of the part and the land burnishes the surface of the part to form a highly reflective and smooth surface. Thus, the diamond cutter cuts and burnishes portions of the part, thereby eliminating a subsequent polishing step.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a continuation of U.S. patent application Ser. No. 13/610,835filed Sep. 11, 2012 entitled “Methods For Cutting Smooth ReflectiveSurfaces”, which claims priority to U.S. Provisional Patent ApplicationNo. 61/689,170, filed May 29, 2012, and entitled “Component For AnElectronic Device,” each of which is incorporated herein by reference inits entirety and for all purposes.

FIELD

The described embodiments relate generally to cutting and to surfacefinishing. More specifically, methods and tools for cutting a highlyreflective and smooth surface on a finished product.

BACKGROUND

Many consumer products such as electronic devices have surfaces that arefabricated from metal. In many cases, these metal surfaces are shiny andreflective so as to enhance the look and feel of the products. Ingeneral, the smoother the metal surface, the more reflective it is.These metal surfaces are often polished to rub or chemically reduce theamount of irregular topography of the metal surface to leave a smootherprofile, and thus a shinier surface.

In some cases, the metal surfaces can include sharp edges and features.Since standard polishing techniques typically reduce the overalltopography of the metal surface, these standard polishing techniques canalso erode the sharp edges leaving rounded or tapered features.

Therefore, providing a device and method for producing a highlyreflective metal surface while keeping the integrity of the workpiecegeometry, especially at sharp edges, is desired.

SUMMARY

This paper describes various embodiments that relate to cutting andfinishing a surface using a cutter capable of cutting and burnishing asurface. Methods described are useful for cutting and providing a highlyreflective and smooth surface to a part, such as an enclosure for anelectronic device. The cutting methods can be used to cut metal ornon-metal surfaces. In some embodiments, methods involve cutting a parthaving substantially horizontal and vertical surfaces. For example,methods described can be used to cut chamfered portions along an edge ofan enclosure for an electronic device. The highly reflective and smoothsurface can then be provided a protective layer, such as an anodizationlayer.

In described embodiments, the cutter has a cutting edge, a heel and aland disposed between the cutting edge and heel. In some embodiments,the cutter is made of diamond material, such as mono crystalline diamondor poly crystalline diamond. The cutter can be used with a millingmachine where the cutter contacts a workpiece a number of times witheach rotation of the spindle of the milling machine. The cutting edgecuts the surface of the workpiece and the land burnishes the surface ofthe workpiece to form a highly reflective and smooth surface. In someembodiments the heel of the cutter can also burnish the surface of theworkpiece. Thus, the cutter can cut and burnish portions of theworkpiece in one operation, thereby eliminating a subsequent polishingstep.

According to one embodiment, a method of cutting a part using a diamondcutter is described. The diamond cutter has a cutting edge and a land.The method involves cutting a first surface of the part using thecutting edge to form a second surface having a number of peaks andtroughs. The peaks reduce the overall reflectiveness and smoothness ofthe second surface. The method also involves burnishing the secondsurface using the land to remove substantially all the peaks to form athird surface, which is highly reflective and smooth. The cutting andburnishing includes a milling operation where the diamond cutter iscoupled to a milling machine. The diamond cutter is rotated about aspindle of the milling machine such that the diamond cutter contacts thepart with each rotation of the spindle.

According to another embodiment, a method of forming a highly reflectiveand smooth metal surface on a part using a diamond cutter is described.The diamond cutter includes a cutting edge and a land. The methodinvolves forming a first anodization layer on a first metal surface ofthe part. The part includes a first surface having a substantiallyvertical portion and a substantially horizontal portion. The firstanodization layer is formed on least portions of the substantiallyvertical and substantially horizontal portions. The method also involvescutting a section of the first anodization layer and a section of metalunderlying the first anodization layer using the cutting edge of thediamond cutter to form a second surface having a number of peaks andtroughs. The peaks reduce the overall reflectiveness and smoothness ofthe second surface. The method also involves burnishing the secondsurface using the land of the diamond cutter to remove substantially allthe peaks to form a third surface, which is highly reflective andsmooth. The cutting and burnishing includes a milling operation wherethe diamond cutter is coupled to a milling machine and the diamondcutter is rotated about a spindle of the milling machine such that thediamond cutter contacts the part with each rotation of the spindle. Themethod additionally involves forming a second anodization layer on atleast the third highly reflective and smooth surface.

According to an additional embodiment, a method of forming a reflectiveand smooth surface on a part using a diamond cutter is described. Thediamond cutter includes a cutting edge and a land. The method involvesforming a first anodization layer on a first surface of the part. Themethod also involves cutting a section of the first anodization layerand a section of metal underlying the first anodization layer using thecutting edge to form a second surface having a number of peaks andtroughs. The peaks reduce the overall reflectiveness and smoothness ofthe second surface. The method additionally involves burnishing thesecond surface using the land to remove substantially all the peaks toform a third surface, which is highly reflective and smooth. The cuttingand burnishing include a milling operation where the diamond cutter iscoupled to a milling machine. The diamond cutter is rotated about aspindle of the milling machine such that the diamond cutter contacts thepart with each rotation of the spindle. The method further involvesforming a second anodization layer on at least the third highlyreflective and smooth surface.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a diamond cutting tool assembly in accordance withdescribed embodiments.

FIGS. 2A and 2B illustrate additional configurations of diamond cuttingtool assemblies in accordance with described embodiments.

FIG. 3 illustrates two perspective side views of a diamond cutting toolin accordance with described embodiments.

FIGS. 4A and 4B illustrate perspective side views of an insert and shankportions of a diamond cutting tool in accordance with describedembodiments.

FIG. 5 illustrates a diamond cutter during a cutting procedure inaccordance with described embodiments.

FIGS. 6A and 6B illustrate a selected profile of a part undergoing acutting procedure in accordance with described embodiments.

FIGS. 7A-7D illustrate selected profiles of two separate partsundergoing cutting procedures using two different diamond cutting toolsin accordance with described embodiments.

FIGS. 8A and 8B illustrate diamond cutters undergoing two differentalignment procedures in accordance with described embodiments.

FIG. 9 is a flowchart illustrating a process which includes a cuttingprocess graphically presented in FIGS. 10A-10D.

FIGS. 10A-10D graphically illustrate selected profiles of a partundergoing a cutting process described in the flowchart of FIG. 9.

FIG. 11 is a schematic isometric view of a portable electronic deviceconfigured in accordance with an embodiment of the disclosure.

FIG. 12 is a schematic isometric view of at least a portion of asubassembly of the electronic device of FIG. 11.

DETAILED DESCRIPTION

The following disclosure describes various embodiments of electronicdevices, such as portable electronic devices including, for example,mobile telephones. Certain details are set forth in the followingdescription and Figures to provide a thorough understanding of variousembodiments of the present technology. Moreover, various features,structures, and/or characteristics of the present technology can becombined in other suitable structures and environments. In otherinstances, well-known structures, materials, operations, and/or systemsare not shown or described in detail in the following disclosure toavoid unnecessarily obscuring the description of the various embodimentsof the technology. Those of ordinary skill in the art will recognize,however, that the present technology can be practiced without one ormore of the details set forth herein, or with other structures, methods,components, and so forth.

Representative applications of methods and apparatus according to thepresent application are described in this section. These examples arebeing provided solely to add context and aid in the understanding of thedescribed embodiments. It will thus be apparent to one skilled in theart that the described embodiments may be practiced without some or allof these specific details. In other instances, well known process stepshave not been described in detail in order to avoid unnecessarilyobscuring the described embodiments. Other applications are possible,such that the following examples should not be taken as limiting.

In the following detailed description, references are made to theaccompanying drawings, which form a part of the description and in whichare shown, by way of illustration, specific embodiments in accordancewith the described embodiments. Although these embodiments are describedin sufficient detail to enable one skilled in the art to practice thedescribed embodiments, it is understood that these examples are notlimiting; such that other embodiments may be used, and changes may bemade without departing from the spirit and scope of the describedembodiments.

In the detailed description, reference is made to cutting a workpiece orpart. In certain embodiments, the part can be made of metal, such asaluminum or aluminum alloy. However, a person of skill in the art wouldrecognize that in the context of the present technology, the term partcan refer to any suitable material capable of undergoing a cuttingprocedure to form a highly reflective surface, including metal, plastic,glass, and so forth.

The embodiments described herein relate to methods, systems, andstructures for forming a highly reflective surface cut into a part. Inthe described embodiments, a diamond cutter is used to cut a surface ofthe part. The diamond cutter can be a poly crystalline diamond (PCD) ora mono crystalline diamond (MCD). In described embodiments, the diamondcutter has a cutting edge, a land and a heel. The cutting edge removessurface material from the surface of the part to form a second scallopedsurface having peaks and troughs, the peaks reducing the overallreflective or smooth appearance of the second surface. The land, andoptionally heel, subsequently burnishes the second surface by reducingthe peaks to form a highly reflective and smooth finished surface. Thus,the diamond cutter simultaneously cuts and burnishes portions of thepart, eliminated the need for an additional polishing step. In preferredembodiments, the diamond cutter is configured to have a relatively longcutting radius, which results in the smoother highly reflective finishedsurface.

In described embodiments, a diamond cutter is mounted in a machiningtool, such as a computerized numerical control (CNC) machining tool, forcutting a part. In certain embodiments a diamond cutter is configured tobe used in a milling machine, wherein the diamond cutter is rotated in acircular motion around a spindle axis and moved along the workpiecesurface to contour the surface of the workpiece. FIG. 1 shows a cuttingtool assembly 100 in accordance with described embodiments. As shown,cutting tool assembly 100 includes tool holder 106 and cutting tool,which includes diamond cutter 102 and shank 104. Diamond cutter 102 iscoupled to shank 104 using, for example, a brazing procedure. Shank 104is configured to removably fit into tool holder 106, which is in turnconfigured to be positioned in a milling machine (not shown). Cuttingtool assembly 100 is positioned to cut workpiece 108, which can besecured using any of a number of suitable methods, such as by use of aclamp. During a cutting operation, cutting tool assembly 100 rotatesabout spindle axis 110 while secured workpiece 108 is moved towarddiamond cutter 102. In alternative embodiments, cutting tool assemblycan be moved toward secured workpiece 108. The cutting edge of diamondcutter 102 is positioned at a cutting radius 112 from the spindle axis110. With each rotation of the spindle, diamond cutter 102 takes a cutat the surface of workpiece 108. During a milling cutting operation, thecutting edge of diamond cutter 102 enters and exits workpiece 108 anumber of times, also known as interrupted cutting. This interruptedcutting can produce a scalloped surface on workpiece 108, which candiminish the overall reflective or smooth appearance of the cut surface.The cutting tool and methods described herein can reduce the amount ofscalloped surface on workpiece 108, thereby forming a highly reflectiveand smooth finished surface on workpiece 108. Details regarding reducinga scalloped surface in accordance with embodiments will be describedbelow.

FIGS. 2A and 2B illustrate additional configurations of cutting toolassemblies in accordance with described embodiments. At FIG. 2A, diamondcutter 202 is coupled to shank 204, which is in turn removably coupledto tool holder 206. Tool holder 206 is configured to be mounted in amilling tool (not shown). In this case, shank 204 is positioned in toolholder 206 such that the length of shank 204 is substantially parallelto the spindle axis of rotation 226. Workpiece 208 is positioned suchthat diamond cutter 202 can cut the surface if workpiece 208. At FIG.2B, holder 210 is configured to hold two shanks 214 and 216, each ofwhich have diamond cutters 218 and 220, respectively, disposed thereon.In this case, both shanks 214 and 216 are substantially perpendicular tospindle axis of rotation 226. Diamond cutter 218 is positioned to cutworkpiece 222 and diamond cutter 220 is positioned to cut workpiece 224.In one embodiment, workpiece 222 and 224 are the same workpiece anddiamond cutters 218 and 220 cut workpiece 222/224 at different times.For example, diamond cutter 218 can cut a first portion of workpiece222/224. Next, workpiece 222/224 can be re-positioned in front ofdiamond cutter 220 and diamond cutter 200 can cut a second portion ofworkpiece 222/224.

FIG. 3 illustrates two perspective side views of a diamond cutting tool300 in accordance with some embodiments of the disclosure. Cutting tool300 includes shank 302 and diamond cutter 304. Diamond cutter 304 ismechanically coupled to shank 302 using, for example, a brazingprocedure. The brazing procedure typically uses an alloy filler metal,such as silver containing filler alloy. As shown, diamond cutter 304 ispositioned on the end of cutting tool 300 such that cutting edge 306,land 308 and optionally heel 310 can contact the workpiece duringcutting. Shank 302 is preferably made from a rigid material, such ascarbide, to rigidly maintain the position of cutting tool 300 duringcutting, thereby allowing a smoother finished cut to be made. The shapeof shank 302 can vary to maximize rigidity during the cutting procedure.The length of shank 302 can in part determine the cutting radius duringcutting of a workpiece. Shank 302 can be configured to be mechanicallycoupled to a tool holder (not shown) which is attached to a spindle of amilling machine (not shown), which spins cutting tool 300 at highspeeds. In certain embodiments, cutting tool 300 is positioned in a toolholder (not shown) such that the cutting radius is relatively large. Byusing a relatively large cutting radius, cuts made by cutting tool 300can have relatively less scalloped portions, which will be discussed indetail below with reference to FIGS. 7A-7D. As cutting tool 300 is heldrigidly in place by shank 302 within a tool holder (not shown), thecutting angle relative to the workpiece can stay steady.

FIGS. 4A and 4B illustrate alternative embodiments of a cutting tool inaccordance with the present technology. FIG. 4A shows two perspectiveviews of an insert piece 400. Diamond cutter 402 is mechanically coupledto insert piece 400 at on end using, for example, a brazing procedure.The brazing procedure can use an alloy filler metal, such as silvercontaining filler alloy. Diamond cutter 402 is positioned on the end ofinsert piece 400 such that the heel, land and optionally heel cancontact the workpiece during cutting. FIG. 4B shows shank 410 which canbe connected to insert piece 400 using, for example, bolts to form thefinished cutting tool. The cutting tool can then be inserted in themachining tool similarly to cutting tool 300 of FIG. 3.

As described above, embodiments of the disclosure involve the use of adiamond cutter which can be made of a polycrystalline diamond (PCD) or amono crystalline diamond (MCD). In general, diamond is arranged in acubic crystalline lattice system, in which carbon atoms are covalentlybonded. The extremely high bond and lattice energy of diamond makes itextremely hard therefore a better cutting material than metals orcarbides, for example. Two forms of diamond are polycrystalline diamond(PCD) and monocrystalline diamond (MCD). PCD is made up of many smallindividual crystals bound together with a binder material, such as acobalt binder. Cutting tools made of PCD can have a somewhat serratededge due to the boundaries where the individual crystals are boundtogether. PCD cutting tools are often described by the average size ofthe crystals, also called grain size, and type of binder. When a PCD isused to cut a surface, marks from the cutting edge can appear on thesurface which correspond to the grain boundaries between the crystals.These marks typically appear as lines on the workpiece surface. Incontrast MCD is one continuous crystal which does not have grainboundaries. Since MCD does not have grain boundaries, it does not leavegrain boundary marks from the cutting edge as in the case with PCD. Itshould be noted, however, that in a milling operation, both PCD and MCDcutters can leave marks due to an interrupted cut during the millingprocess. As described above, an interrupted cut is due to the cuttercontacting the workpiece surface at each rotation of the spindle. Theinterrupted cutting can leave a scalloped surface on the workpiece.

In order to lessen the scalloped portions of a cut surface and toproduce a highly reflective and smooth finished surface, embodiments ofthe present disclosure include a diamond cutter having featuresgraphically illustrated in FIG. 5. The top view and close up inset viewsillustrated in FIG. 5 show diamond cutter 504 cutting workpiece 502.Diamond cutter 504 includes three surfaces: rake face 514; land orprimary clearance 506; and secondary clearance 508. Diamond cutter 504is mechanically coupled to a shank (not shown), which is in turnmechanically coupled to a toll holder (not shown), which is in turnmechanically coupled to a milling machine (not shown). Cutting edge 510of diamond cutter 504 rotates around the spindle axis of the millingmachine at a cutting arc 522. Cutting arc 522 is a function of thecutting radius (e.g., 112 of FIG. 1) from the cutting edge 510 to thespindle axis (e.g., 110 of FIG. 1). Diamond cutter 504 can contactworkpiece 502 at cutting edge 510, land 506 and heel 512. Since cuttingedge 510, land 506 and heel 512 can come into contact with workpiece 502during cutting, it is advantageous for these surface to be substantiallyfree of defects caused, for example, by a lapping or polishing procedurein the manufacturing process of the diamond cutter. In preferredembodiments, cutting edge 510, land 506 and heel 512 have minimal visualimperfections such as lapping or polishing chips. In one embodiment fora MCD cutter, the cutting edge, land and heel have no visibleimperfections at 500× magnification. In one embodiment for a PCD cutter,the cutting edge, land and heel have no visible imperfections at 100×magnification. It should be understood that lower or higher qualitydiamond cutters with greater or fewer imperfections can be used. Factorssuch as cost, availability and type of diamond cutters can be consideredwhen determining the quality of diamond cutter used in a particularapplication. For example, an MCD cutter with a high quality cutting edge(e.g., very few visible imperfections) can be used in applications wherethe resultant cut surface is at a highly visible portion of anelectronic device. A PCD cutter can be used, for example, inapplications where the resultant cut surface can be slightly obscuredby, for example, a dark anodizing film.

Before a cutting operation begins, diamond cutter 504 can be alignedsuch that the cutting edge 510 contacts workpiece 502 and effectiveprimary clearance angle 518 puts land 506, and optionally heel 512, intocontact with workpiece 502. Example alignment procedures will bediscussed in detail below with reference to FIGS. 8A and 8B. Duringcutting, diamond cutter 104 proceeds in the travel direction as show inFIG. 5. First, cutting edge 510 cuts the surface of workpiece 502resulting in a second surface with peaks and troughs. Next, land 506,and optionally heel 512, can come into contact with workpiece 502burnishing the surface and removing substantially all the peaks of thesecond surface, thereby providing a highly reflective and smoothfinished surface on workpiece 502. The degree in which the peaks areremoved depends on the amount of burnishing the land and heel impart onthe surface. Details regarding removal of peaked portions of a scallopedsurface in accordance with embodiments will be described below withreference to FIGS. 6A and 6B. Since the surface is highly reflective andsmooth, there is no need for a subsequent traditional polishing process.In this way an entire polishing step can be removed from themanufacturing process. Note that in some embodiments, the effectiveprimary clearance can be backed off the surface of workpiece 502 a smallamount before cutting begins. In this backed off configuration, portionsof land 506 can still come into contact and burnish workpiece 502 due toelastic recovery of workpiece 502 material during the cutting process.Using the cutter in this backed off configuration can extend thelifetime of diamond cutter 504.

As discussed above, after a cutting edge of a diamond cutter cuts thesurface of a workpiece, a scalloped surface can remain on the workpiece.To illustrate this graphically, reference will now be made to FIGS. 6Aand 6B, which show cross sections of a surface of a workpiece undergoinga cutting procedure in accordance with described embodiments. In FIG.6A, workpiece 600 has undergone cutting from only the cutting edge (510in FIG. 5), leaving a second surface with peaks 604 and troughs 602.Peaks 604 can be caused by interrupted cutting due to the millingprocess as described above. In FIG. 6A, peaks 604 protrude a height 606from trough 602. In FIG. 6B, workpiece 600 has been contacted by theland, and optionally heel, (506 and 512, respectively, in FIG. 5)reducing substantially all the height 606 of peaks 604, leaving a highlyreflective finished surface 608. It is noted that there still can beremaining slightly protruding portions 610 on highly reflective andsmooth finished surface 608, depending on the amount of burnishing (i.e.amount of rubbing), however surface 608 is generally highly reflectiveand smoothed to a mirror shine and generally does not require furtherpolishing.

In order to obtain as smooth as possible highly reflective and smoothfinished surface, in some embodiments the cutting radius (112 of FIG. 1)is relatively long. To illustrate graphically how the cutting radiuseffects the overall smoothness of the resulting surface, reference willnow be made to FIGS. 7A-7D which show side views of two differentworkpieces undergoing cutting from two different diamond cutters inaccordance with the described embodiments. FIGS. 7A and 7B showworkpiece 700 undergoing a cutting procedure using an diamond cutterwith a short cutting radius, and FIGS. 7C and 7D show workpiece 712undergoing a cutting procedure using an diamond cutter with a longcutting radius.

At FIG. 7A, workpiece 700 has undergone cutting from the cutting edge ofa diamond cutter assembly having a short cutting radius. That is, thedistance between the cutting edge and the spindle axis is relativelyshort. After only cutting edge cuts workpiece 700, a second scallopedsurface 708 with peaks 704 and troughs 702 is formed. Peaks 704 can becaused by the interrupted cutting due to milling process. The distance706 between the peaks 704 is directly proportional to the cutting radiusof the diamond cutting assembly. At FIG. 7B, workpiece 700 has beencontacted by the land, and optionally the heel, reducing substantiallyall the height 722 of peaks 704, leaving a highly reflective and smoothfinished surface 709 with remaining slightly protruding portions 710which diminish the overall reflective and smooth appearance of a highlyreflective and smooth finished surface 709.

At FIG. 7C, workpiece 712 has undergone cutting from the cutting edge ofa diamond cutter assembly having a short cutting radius. That is, thedistance between the cutting edge and the spindle axis is relativelylong. After only cutting edge cuts workpiece 712, a second scallopedsurface 720 with peaks 716 and troughs 714 is formed. Since the distance718 between the peaks 716 is directly proportional to the cutting radiusof the diamond cutting assembly, distance 718 is longer than distance706 of workpiece 700 at FIG. 7A. Thus, second surface 720 has a smallerportion having peak 716 compared to the second surface 708 of FIG. 7A.At FIG. 7D, workpiece 712 has been contacted by the land, and optionallythe heel, reducing substantially all the height 724 of peaks 716,leaving a highly reflective and smooth finished surface 720 withremaining slightly protruding portions 722. Note that there are lessremaining slightly protruding portions 722 in the highly reflective andsmooth surface 720 compared to remaining slightly protruding portions712 in the highly reflective and smooth surface 721. Therefore, using adiamond cutter assembly having a longer cutting radius can provide animproved overall highly reflective and smooth finished surface. In oneembodiment the diamond cutter assembly has a cutting radius about 35millimeters.

Since the cutting procedures described in the present technologyrequires a high level of accuracy regarding the surface geometry of theworkpiece, the cutting tool should be aligned at a high level ofaccuracy relative to the workpiece surface before the cutting processbegins. It can be difficult to manufacture diamond cutter to meetextremely high levels of specified dimensional and defect freespecifications. Therefore, embodiments of the disclosure involvecalibration procedures to compensate for any imperfections in thegeometric dimensions of the diamond cutter. In one embodiment,calibration involves calibrating the cutter directly on the workpiecesurface wherein the cutter is rotated until the cutting edge, land andheel (510, 506 and 512, respectively, in FIG. 5) contact the workpiecesurface. In other embodiments, calibration involves rotating the cuttertool until the land (506 in FIG. 5) provides sufficient burnishing tothe workpiece surface.

FIGS. 8A and 8B illustrate two different alignment or calibrationprocedures to optimize the amount and effectiveness of burnishing inaccordance with described embodiments. In both FIGS. 8A and 8B, thediamond cutter is initially positioned in the milling machine forcutting. At FIG. 8A, diamond cutter 802 is calibrated by controlling thedifference in length between first line 804 from spindle axis 808 tocutting edge 810, and a second line 812 from spindle axis 808 to heel818. The length of first line 804 (R1) is measured and the length ofsecond line 812 (R2) is measured. Measurement can be accomplished byusing, for example, laser generated reference lines (shown by dottedlines). Next, a cutting operation is performed on a workpiece (notshown) using the R1 and R2 parameters. After the cutting operation iscomplete, the workpiece is inspected to determine the quality of cut,i.e., the reflectiveness and smoothness of the resulting cut surface.Next, the position of diamond cutter 802 is moved such that R1 is longeror shorter, i.e., land 814 and heel 818 are farther or closer to cuttingarc 816. The bigger R2 is compared to R1, the more land 814 and heel 818will rub the workpiece and the more burnishing the workpiece willexperience. In this way, controlling the difference between R1 and R2can control the amount of burnishing. In preferred embodiments, thedifference between R1 and R2 are optimized to allow land 814 and/or heel818 to sufficiently burnish the surface of the workpiece, but not rub sohard as to provide too much friction during cutting. Next, anothercutting operation is performed and the workpiece is again inspected forquality of cut. If the quality of cut is not of an acceptable quality,the re-positioning of the diamond cutter 802, cutting and inspecting isrepeated until an acceptable quality cut is achieved.

At FIG. 8B, diamond cutter 820 is positioned within the tool holder (notshown) by controlling the angle between reference line 822 from cuttingedge 824 to spindle axis 832 and the land 826. Reference line 822 can begenerated by using, for example, a laser generated line (shown by dottedline). Next, a cutting operation is performed on a workpiece (not shown)using a theta angle 834 parameter. After the cutting operation iscomplete, the workpiece is inspected to determine the quality of cut,i.e., the reflectiveness and smoothness of the resulting cut surface.Next, the position of diamond cutter 820 is moved such that theta 834 islarger or smaller, i.e., land 826 and heel 828 are farther or closer tocutting arc 830. The farther outside land 826 and heel 828 are to arc830, the more land 826 and heel 828 will rub the workpiece and the moreburnishing the workpiece will experience. In this way, controlling theangle theta can control the amount of burnishing. As with the alignmentprocedure shown in FIG. 8A, theta angle parameter 834 can be optimizedto allow land 826 and heel 828 to sufficiently burnish the surface ofthe workpiece, but not rub so hard as to provide too much frictionduring cutting. As with the alignment procedure described for FIG. 8Aabove, the cutting, re-positioning and inspection can be repeated untilan acceptable quality of cut is achieved.

During the alignment procedures shown in FIGS. 8A and 8B, in someembodiments the amount of burnishing can be backed off the cuttingradius a small amount before cutting begins. As discussed above withreference to FIG. 5, use of the diamond cutter in a backed offconfiguration can extend the lifetime of diamond cutter. In this backedoff configuration prior to cutting, the heel does not touch theworkpiece. However, during cutting the land can still come into contactwith and burnish the surface of the workpiece due to elastic recovery ofthe workpiece material. Factors such as diamond cutter lifetime, desiredamount of burnishing and amount of diamond cutter friction on theworkpiece can be considered when optimizing the alignment of the cuttingtool.

In described embodiments, the part can be cut at a substantially flatsurface portion of the part wherein the substantially flat surface isgiven a highly reflective and smooth finish. Alternatively, the part canbe cut at a portion of the part that has a feature with horizontal,vertical and angled surfaces. The diamond cutter can cut the feature toform a different feature that has a highly reflective and smoothfinished surface. For instance, a chamfer may be cut at a corner or edgeof a workpiece. The resulting chamfer will have a highly reflective andsmooth finished surface in accordance with the described embodiments. Inorder to protect the highly reflective and smooth surface, an optionaltransparent coating or plating can be formed thereon. In certainembodiments, the transparent coating is an anodization layer that issubstantially clear, thereby allowing the highly reflective surface tobe visible through the anodization layer. FIGS. 9 and 10A-10D illustratesteps involved in a process of forming a feature with a highlyreflective and smooth surface into a part in accordance with embodimentsof the technology. FIG. 9 is a flowchart detailing process steps andFIGS. 10A-10D graphically present side views of a portion of a metalpart undergoing the process described in FIG. 9. In the followingnarrative, reference will be made to the flowchart of FIG. 9 inconjunction with the side view presentations of FIGS. 10A-10D.

Process 900 begins at 902 (corresponding to FIG. 10A) where part 1000 iscut to have a first surface with vertical 1002 and horizontal 1004portions. In FIG. 10A, the first surface has an edge 1006. Part 1000 canbe cut using any number of suitable cutting procedures such as amachining procedure to form the shape of part 1000. It should be notedthat substantially vertical 1002 and a horizontal 1004 portions in FIG.10A-10D can form a edge 1006 having any angle, including a 90 degreeangle. In addition, vertical 1002 and a horizontal 1004 portions can besubstantially flat or they may be curved. The part can then undergooptional surface treatments such as polishing and/or addition of artwork(e.g., company logo and/or text) using, for example, a photolithographyprocess. In one embodiment, a blasting operation can be performedwhereby the part is exposed to blasting media to create a rough blastedsurface over the part.

At 904 (corresponding to FIG. 10B), part 1000 undergoes an optionalfirst anodization process to form a first anodization layer 1008 thatcovers at least portions of vertical 1002 and horizontal 1004 surfacesof part 1000 near edge 1006. Anodization layer 1008 serves to protectthe metal surface of part 1000 from corrosion and scratching. Sinceanodizing is a conversion process that involves converting at least aportion of part 1000 to a corresponding metal oxide, the anodizingprocess forms a first interface surface 1016 and second interfacesurface 1018 between first anodization layer 1008 and part 1000. Firstinterface surface 1016 has a topology in accordance with the topology ofhorizontal portion 1002 prior to anodizing. Likewise, second interfacesurface 1018 has a topology in accordance with the topology of verticalportion 1004 prior to anodizing. In one embodiment, first anodizationlayer 1008 is approximately 8 to 12 microns thick and is substantiallyopaque so that the underlying metal of part 1000 is not substantiallyvisible through first anodization layer 1008. Note that due to stressbuild up at edge 1006, first anodization layer 1008 can have cracks1010.

At 906 (corresponding to FIG. 10C), a portion of the optional firstanodization layer 1008 and a portion of metal part 1000 is cut using adiamond cutter described above to form a second surface 1012 (which canalso be referred to as a chamfer), which is highly reflective andsmooth. In certain embodiments, a portion of the optional firstanodization layer 1008 and a portion of metal part 1000 are given arough cut using a different cutting tool prior to using a diamond cuttertool. The rough cut can be made so as to remove a bulk amount ofmaterial before diamond cutter is used in accordance with describedembodiments. The rough cut can be made using a suitable cutting toolsuch as a carbide or a metal cutter or a diamond cutter of lesserquality than the diamond cutter used to cut a highly reflective andsmooth surface as described above. As described above, a smooth surfacehas a regular topology and can therefore be referred to as being flat orhaving an even topology. Thus, the cutting process provides a secondsurface 1012 that is flatter and has a more even topology than a surfacethat is not cut using such techniques, such as each of horizontalsurface 1004 and vertical surface 1002 prior to anodizing. In FIG. 10C,the second surface is a chamfer. It should be noted that second surface1012 can be cut at any angle relative to the horizontal 1004 andvertical 1002 portions. For example, second surface 1012 can be cut at a45 degree angle relative to one of horizontal 1004 and vertical 1002portions. Since second surface 1012 has a highly reflective and smoothsurface, there is no need for subsequent polishing. This isadvantageous, not only because it removes an extra step in the process,but also because traditional polishing techniques such as mechanical andchemical polishing, can erode features of the part. In particular,traditional polishing techniques can erode and round off sharp edges andcorners such as the edges of chamfer 1012, reducing the aesthetic appealof the part.

At 908 (corresponding to FIG. 10D), part 1000 undergoes an optionalsecond anodization process to form a second anodization layer 1014substantially only on and to protect the highly reflective and smoothsecond surface 1012 (which can also be referred to as a chamfer). Theanodizing process forms a third interface surface 1020 (which can bereferred to as a chamfer interface surface) between second anodizationlayer 1014 and part 1000. Third interface surface 1020 has a topology inaccordance with the topology of second surface 1012 prior to anodizing.Thus, third interface surface 1020 takes on a smooth and even topologyin accordance with second surface 1012. For example, if second surface1012 has a mirror shine, third interface surface 1020 can take on themirror shine. In this way, third interface surface 1020 has a more eventopology (smoother and flatter) than each of first interface surface1016 and second interface surface 1018. It should be noted that thesecond anodization process can use different process parameters than thefirst anodization process described previously, forming secondanodization layer 1014 with different physical characteristics thanfirst anodization layer 1008. For example, second anodization layer 1014can be substantially transparent in order to allow the underlying highlyreflective and smooth chamfer 1015 to be viewable. In addition, thesecond anodization layer 1014 can be formed such that there is a clearlydefined interface between first anodization layer 1008 and secondanodization layer 1014 (shown by an angle in FIG. 10D). After process900 is complete, the finished part in FIG. 10D has a highly reflectiveand smooth chamfer 1012 with sharply defined and cosmetically appealingedges.

As discussed previously, tools and methods of the described embodimentscan be applied in the fabrication of electronic devices, including forexample, personal computers and portable tablets and phones. FIG. 11 isa schematic isometric view of a portable electronic device 10(“electronic device 10”), such as a mobile telephone, configured inaccordance with an embodiment of the disclosure. In the illustratedembodiment, the electronic device 10 includes a body 11 carrying adisplay 12 that allows a user to interact with or control the electronicdevice 10. For example, the display 12 includes a cover or cover glass14 that is operably coupled to a frame, housing, or enclosure 16. Incertain embodiments, the display 12 and/or cover glass 14 can includetouch sensitive features to receive input commands from a user.Moreover, in certain embodiments a cover or cover glass can bepositioned on one side of the electronic device 10, or a cover or coverglass can be positioned on opposing sides of the electronic device 10.As described in detail below, the enclosure 16 and the cover glass 14 atleast partially house or enclose several internal features of theelectronic device.

In the embodiment illustrated in FIG. 11, the enclosure 16 also at leastpartially defines several additional features of the electronic device10. More specifically, the enclosure 16 can include audible speakeroutlets 18, a connector opening 20, an audio jack opening 22, a cardopening 24 (e.g., SIM card opening), a front facing camera 26, a rearfacing camera (not shown), a power button (not shown), and one or morevolume buttons (not shown). Although FIG. 11 schematically illustratesseveral of these features, one of ordinary skill in the art willappreciate that the relative size and location of these features canvary.

In certain embodiments, the enclosure 16 can be made from a metallicmaterial. For example, the enclosure 16 can be made from Aluminum, suchas 6063 Aluminum. In other embodiments, however, the enclosure 16 can bemade from other suitable metals or alloys. According to additionalfeatures of the embodiment shown in FIG. 11, the enclosure 16 includesopposing edges identified individually as a first edge portion 30 a anda second edge portion 30 b, extending around a periphery of the body 11.In certain embodiments, one or both of the edge portions 30 can have achamfered or beveled profile. As described in detail below, thechamfered edge portions 30 can be processed relative to the enclosure 16to provide an aesthetically appealing appearance. For example, theexterior surface of the enclosure 16 can be treated and the edgeportions 30 can subsequently be treated. In one embodiment, for example,a first anodization process can be applied to the enclosure 16 and asecond subsequent anodization process can be applied to the edgeportions 30. Additional suitable surface treatments, includingintermediary surface treatments, can be applied to the enclosure 16and/or the edge portions 30. In still further embodiments, the edgeportions 30 can have other suitable profiles or shapes including and/orsurface treatments.

FIG. 12 is a schematic isometric view of at least a portion of asubassembly 40 of the electronic device of FIG. 11. In the embodimentillustrated in FIG. 12, the subassembly 40 includes the enclosure 16coupled to a cover glass, such as the cover glass 14 shown in FIG. 11.As shown in FIG. 12, the enclosure 16 includes a first enclosure portion42 coupled to a second enclosure portion 44, which is in turn coupled toa third enclosure portion 46. More specifically, the enclosure 16includes a first connector portion 48 that couples the first enclosureportion 42 to the second enclosure portion 44. The enclosure alsoincludes a second connector portion 50 that couples the second enclosureportion 44 to the third enclosure portion 46. In certain embodiments,the first, second, and third enclosure portions 42, 44, and 46 can bemetallic and the first and second connector portions 48, 50 can be madefrom one or more plastic materials. As described below in detail, forexample, each of the first and second connector portions 48, 50 can beformed from a two shot plastic process that includes a first plasticportion that joins the corresponding enclosure portions and a secondcosmetic plastic portion that at least partially covers the firstplastic portions. As further described in detail below, these plasticportions can be configured to withstand harsh manufacturing processesand chemicals that may be used to form and process the enclosure. Infurther embodiments, the enclosure portions 42, 44, and 46 and/or theconnecting portions 48, 50 can be made from other suitable materialsincluding metallic, plastic, and other suitable materials.

According to additional features of the embodiment illustrated in FIG.10, the enclosure 16 can include one or more low resistance conductiveportions 52 (shown schematically) for grounding purposes. Conductiveportions 52 can include, for example, of aluminum which can shield RFwaves. The conductive portion 52 can be formed by removing one or morelayers or portions of the enclosure 16 to provide a lower resistancethrough the enclosure 16 for antenna transmissions or communications. Incertain embodiments, for example, the conductive portion 52 can beformed by laser etching or otherwise removing or etching an anodizedportion of the enclosure 16.

The illustrated subassembly 40 also includes several inserts 54 thatprovide increased structural connection strength relative to theenclosure 16. In embodiments where the enclosure 16 is formed fromAluminum, for example, the inserts 54 can provide increased strength anddurability. More specifically, in certain embodiments the inserts 54 caninclude titanium threaded inserts or nuts that are configured tothreadably engage a corresponding fastener. Titanium inserts 54 can beadvantageous in that the titanium material can withstand harshmanufacturing processes and chemicals. In other embodiments, however,the inserts 54 can be made from other suitable materials including, forexample, steel, brass, etc.

According to yet additional features of the subassembly 40 shown in FIG.12, and as described in detail below, the cover glass 14 can be securelycoupled and/or offset (if desired) relative to the enclosure 16. Morespecifically, the cover glass 14 can be aligned with a reference planeor datum relative to the enclosure 16, and the enclosure 16 (and morespecifically the first enclosure portion 42, the second enclosureportion 44, and/or the third enclosure portion 46) can include one ormore access opening 56 to urge or bias the cover glass 14 relative tothe enclosure 16 for secure attachment (e.g., adhesive attachment) whilemaintaining relatively tight tolerances between the coupled portions.

According to additional embodiments of the disclosure, and as describedin detail below, the cover glass 14 can be made from a glass, ceramic,and/or glass-ceramic material. In one embodiment, for example, the coverglass 14 can be made from a glass with specific portions or volumes ofthe glass formed with ceramic properties. In other embodiments, however,the cover glass 14 can be formed from alumina silica based pigmentedglass.

The foregoing description, for purposes of explanation, used specificnomenclature to provide a thorough understanding of the describedembodiments. However, it will be apparent to one skilled in the art thatthe specific details are not required in order to practice the describedembodiments. Thus, the foregoing descriptions of specific embodimentsare presented for purposes of illustration and description. They are notintended to be exhaustive or to limit the described embodiments to theprecise forms disclosed. It will be apparent to one of ordinary skill inthe art that many modifications and variations are possible in view ofthe above teachings.

What is claimed is:
 1. A metal housing for an electronic device, themetal housing comprising: an edge defined by a first side and a secondside that meet at a chamfer; a first anodization layer positioned on thefirst side and the second side, thereby defining a first interfacesurface between the first side and the first anodization layer, and asecond interface surface between the second side and the firstanodization layer; and a second anodization layer positioned on thechamfer, thereby defining a chamfer interface surface between thechamfer and the second anodization layer, wherein the chamfer interfacesurface has a more even topology than each of the first interfacesurface and the second interface surface such that the chamfer interfacesurface has a higher spectral reflectivity than each of the firstinterface surface and the second interface surface.
 2. The metal housingof claim 1, wherein the edge is along multiple metal portions of thehousing coupled together by plastic connector portions.
 3. The metalhousing of claim 1, wherein the chamfer interface surface includes aplurality of peaks and troughs.
 4. The metal housing of claim 1, whereinthe chamfer interface surface is characterized as having a mirror shine.5. The metal housing of claim 1, wherein an angle between the firstanodization layer on the first side and the second anodization layer onthe chamfer is consistent along the edge of the housing.
 6. The metalhousing of claim 1, wherein the chamfer surface runs continuously alongthe edge and corners of the housing.
 7. The metal housing of claim 1,wherein the first interface surface is substantially perpendicular tothe second interface surface.
 8. The metal housing of claim 1, whereinthe electronic device is a portable telephone.
 9. The metal housing ofclaim 1, wherein the housing has a rectangular shape having two chamferinterface surfaces running along opposing edges of the housing, the edgebeing one of the opposing edges, and the chamfer interface surface beingone of the two chamfer interface surfaces.
 10. The metal housing ofclaim 9, wherein the chamfer interface surface is formed uninterruptedlyalong a corner of the housing, the edge being one of the opposing edges,and the chamfer interface surface being one of the two chamfer interfacesurfaces.
 11. The metal housing of claim 10, wherein the corner iscurved.
 12. A housing for an electronic device, the housing comprising:multiple metal portions coupled by at least one plastic connectorportion, wherein at least one of the metal portions has a first side anda second side that meet at a chamfer, wherein each of the first side andthe second side has a first anodized layer formed thereon, therebydefining a first interface surface between the first side and the firstanodized layer, and a second interface surface between the second sideand the first anodized layer, and wherein the chamfer has a secondanodized layer formed thereon, thereby defining a chamfer interfacesurface between the chamfer and the second anodized layer, wherein thechamfer interface surface has a flatter topology than each of the firstinterface surface and the second interface surface such that the chamferinterface surface spectrally reflects more incident light than each ofthe first interface surface and the second interface surface.
 13. Thehousing of claim 12, wherein the chamfer interface surface runs along anedge and corner portions of the housing.
 14. The housing of claim 13,wherein the corner portions of the housing are curved.
 15. The housingof claim 12, wherein the chamfer interface surface includes a pluralityof peaks and troughs.
 16. The housing of claim 12, wherein the chamferis positioned adjacent a cover glass of the electronic device.
 17. Ahousing for a portable electronic device, the housing comprising: ametal portion having a back and a side wall, wherein the back and theside wall meet at a chamfer, wherein each of the back and the side wallhave a first anodized layer formed thereon such that the back and thefirst anodized layer define a first interface surface positionedtherebetween, and the side wall and the first anodized layer define asecond interface surface positioned therebetween, and wherein thechamfer has a second anodized layer formed thereon such that the chamferand the second anodized layer define a chamfer interface surface,wherein the chamfer interface surface is smoother than each of the firstinterface surface and the second interface surface such that the chamferinterface surface has a higher spectral reflectivity than each of thefirst interface surface and the second interface surface, wherein thefirst anodized layer is more opaque than the second anodized layer. 18.The housing of claim 17, wherein the chamfer interface surface runsalong three metal portions of the housing, the three metal portionscoupled together by two plastic connector portions.
 19. The housing ofclaim 18, wherein two of the three metal portions include corners,wherein the chamfer interface surface runs continuously along at leastone of the corners.
 20. The housing of claim 19, wherein the chamferinterface surface is 45 degrees with respect to each of the firstinterface surface and the second interface surface.